Fuel feed and power control apparatus for combustion engines



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FUEL FEED AND POWER CONTROL APPARATUS FOR COMBUSTION ENGINES Original Filed Sept. 13, 1965 7 Sheets-Sheet 6 r l T0 FVG. 6 f 76 555 70 l l %460 T0 e@ FVG. 6 455/ u w54 457 h 53 465 l s To 407 F/G. 6

Il a 609 ,4i-5** 600 `575 607 564 004 @Aa E 70 563 403 4/3 g @F 5?/72 To" @39 Ff@ G .E 7' PASSAGE' (C4/Z @955559535565 57 566545 030 Ffa@ 600 53759 FG' 5 00/ ',j 504 553 2550 f l E .596 Y FeA/vc/s e. @00a-es e J HOW/:eo L MccoMas Je. 650 (T0 347W@ 6 .,-0 56.07@ II M/KE vv/DEE qF7@ 6 j INVENTORS .3 To PASSAGE 25 65 2715 F/G'. 2 BY AGENT Nov. 8, 1956 F. R. ROGERS ETAL Original Filed Sept. 13, 1963 '7 Sheets-Sheet 7 un 5 6 5 @3g/m I, 534 26635537I G40 5 l( 46 F 667672 o @7/670 635 V465 Y f66 653 /675453 FEA/v E. 660 76 6&5 673 56/ Haw/fea ffmc ggg/ e. 6 674-/ 666 l M/KE w/DEE 347) i 654 @5g INVENTORS u i PI/ J '646 BY f 1 560 65/ 650 AGENT United States Patent O 3,283,500 FUEL FEED AND POWER CONTROL APPARATUS FOR COMBUSTION ENGINES Francis R. Rogers, Howard L. McCombs, Jr., and Mike Snider, all of South Bend, Ind., assignors to The Bendix Corporation, a corporation of Delaware Original application Sept. 13, 1963, Ser. No. 308,799, now Patent No. 3,232,053, dated Feb.' 1, 1966. Divided and this application Oct. 22, 1965, Ser. No. 501,941

Claims. (Cl. 60-39.28)

This is a division of application Serial No. 308,799 filed September 13, 1963 now U.S. Patent No. 3,232,053 issued February 1, 1966.

This invention relates in general to control apparatus for a combustion engine and, in particular, to fuel control apparatus for a gas turbine engine having a variable area exhaust nozzle.

It is an object of the present invention to provide a fuel control for reliably and accurately controlling the ow of fuel to a combustion engine as a function of predetermined engine operating conditions.

It is .another object of the present invention to provide an easily serviced lik'htweight fuel control for an aircraft combustion engine.

It is still another object of the present invention to provide fuel feed an-d power control apparatus having a main fuel control, an afterburner fuel control and a nozzle area control operative together in response to a plurality of variable engine operating conditionsy to maintain fuel feed and exhaust nozzle area within prescribed limits over the entire operating range of the engine as a. function of the variable engine operating conditions.

It is .an important object of the present invention to provide a fuel control having la mechanical computer section and a fuel metering section for an aircraft gas turbine engine which fuel metering section operates on the basis of a constant pressure head across a Variable metering valve area and which computer section operates to receive :a .plurality of input signals representative of variable engine operating conditions such .as engine throttle lever request, engine speed, compressor discharge pressure and compressor inlet air pressure and temperature and mechanically computed control signals therefrom to thereby establish a metering valve area which is a function of one or m-ore of said variable engine operating conditions.

It is yet another object of the present invention to provide fuel feed and power control apparatus for an aircraft gas turbine engine which may be easily modified for operation with different engines of the same type but with varying operating characteristics which must be compensated for bythe fuel -feed land power control apparatus.

Other objects and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein:

FIGURE 1 is a schematic representation of an aircraft jet engine embodying the present invention wherein the component sections of the present invention are shown in block form;

FIGURE 2 is a sche-matic representation showing structural details of ya portion orf the main fuel control shown -in block 4form in FIGURE 1;

FIGURE 3 is a schematic representation showing structural details of the remaining portion of the main fuel control shown in block form in FIGURE 1;

FIGURE 4 is a schematic representation showing structural details of a portion of the afte-rburner fuel control shown in block form in FIGURE l;

FIGURE 4a is a schematic represent-ation showing 3,283,500 Patented Nov. 8, 1966 ice structural details of the .remaining portion of the afterburner fuel control shown in block form in FIGURE l;

FIGURE 5 is a schematic representation showing structural details of a portion of the exhaust nozzle area control sh-own in block form in FIGURE 1; .and

FIGURE 6 is a schematic representation Ishowing structural details of the remaining portion of the exhaust nozzle area contr-ol shown in block form in FIGURE 1.

Referring to FIGURE l, numeral 20 represents an aircraft gas turbine engine of the turbo-fan type which is provi-ded with inner and outer casings 21 .and 22, respectively, which rform :an annular air duct 23 leading from air inlet 24 -to an afterburner section 25 of casing 22 which terminates in a variable area exhaust nozzle 26 having movable exhaust nozzle gates 27. A fan 28 and low pressure air compressor 29 are secured to and driven by a dual turbine 30 via a shaft 31 rotatably carried in bearings, not shown. A high pressure -ai-r compressor 32 in series with compressor 29 is secured to and driven by a turbine 33 via a shaft 34 concentric with shaft 31 and rotatably carried -by hearings, now shown, for independent rotation relative t-o shaft 31. A plurality of combustion ch-ambers 35 is supplied fuel by fuel nozzles 36 connected to :annnular fuel Imanifold 37. A plurality of annular a-fterburner fuel manifold 38, 39 and 40 are arranged to inject Ifuel into duct 23 and/or casing 22 upstream from flame holders 41 which are lsecured to casing 22.

Air flows into inlet 24 and is compressed and displaced rearwardly into duct 23 as well as low pressure air compress-or 29 by fan 28, the compressor 29 pressurizing its associated air flow and delivering the same to the high pressure air compressor 32 which, in turn, further pressurizes the air and discharges to combustion charnbers 35 whe-rein the mixture of fuel and air is burned to form a hot motive gas which flows through turbines 33 Vand 30 driving the same. The hot motive gas is discharged from turbine 30 and together with air exhausted from duct 23 flows through exhaust nozzle 26 and expands to the atm-osphere thereby providing a propelling thrust. Fuel nozzles 42 connected to afterburner fuel manifolds 38, 39 and 40 are .arranged to inject fuel into gas downst-ream of the turbine 33 Where the injected fuel i is burned t-o elevate the temperature of the gas thereby providing a corresponding increase in thrust.

Metered fuel flow is supplied to the fuel manifold 37 from a main fuel control 43 via a fuel conduit 44 connected therebetween. The main lfulel control 43 is supplied pressurized fuel via a Ifuel lsupply conduit 45 leading to a yfuel tank 46 and containing an engine driven positive displacement fuel pump 47. A conventional Igear and shafting arrangement 48 provides a driving connection between the pump 47 and engine shaft 31. Various control input signals associated with engine operation are supplied to the main fuel control 43 which establishes metered fuel ilow to conduit 44 as a function of the various input signals and which .transmits computed pressure signals to other component sections of the system as will i' be `described hereinafter. Among the control input signals are compressor inlet air pressure P1 and temperature T1 which are transmitted to the main fuel control 43 via conduit 49 and temperature pick-up unit 50, respectively, suitably disposed in air inlet 24. The rotational -speed N2 of the 4high .pressure air compressor 32 is transmitted to the ymain Ifuel control 43 via conventional `gearing and shafting arrangement Agenerally indicated by numeral 51. High pressure compressor ldischarge air pressure Pc is transmitted to the main fuel control via conduit 52. A drain passage 53 communicates the interior of the main fuel control 43 with rfuel conduit 45 at fuel pump inlet or drain pressure Po. A manually operative throttle lever 54 movable between cut-olf and :a maximum afterburner position provides a power request signal to the main fuel control 43.

Metered fuel flow is supplied to the lafterburner fuel manifolds 38, 39 and 40 from an after-burner fuel oontrol 55 via fuel conduits 56, 57 and 58, respectively, connected therebetween. The afterbfurner fuel control 55 is supplied pressurized fuel via a fuel supply conduit 59 leading to fuel tank 46 4and containing an engine driven centrifugal fuel pump 60. Among the control input signals supplied to the afterbu-rner fuel control 55 are compressor inlet temperature T1 and compressor discharge air pressure Pc which are supplied via temperature sensing 'uniit 61 and conduit 62, respectively. A drain passage 63 communicates the interior of afterburner fuel control 55 with conduit 53 at fuel pump inlet pressure Po.

The position of the variable area gates 27 is controlled by a power unit which includes a cylinder 64 and a piston y65 slidable therein. Fluid pressure is supplied to opposite sides of the piston 65 via passages. 66 and 68 leading to an lexhaust nozzle control 70 which controls the flow of liuid therethrough as a function of various input control signals. The input control signals include the position of throttle leve-r -54 received via shaft 71 and air pressure P114 and PTY; upstream and downstream of lturbines 33 and 30, respectively, via passages 72 and 73, respectively. The position of gates 27 is transmitted to nozzle control -70 via mechanical feedback mechanism including a spring loaded pulley 74 and flexible link 75 connecting pulley 74 and piston 65. A conduit 76 containing an engine driven fuel pump 76 communicates pressurized fuel to exhaust nozzle control 7 0l from fuel source 46.

VReferring to FIGURES 2 .and 3 which together illusrtrate the various component portions of the main fuel control 43, numeral 77 designates a casing through which fuel flows from supply conduit 45 to fuel conduit 44 via a flow conduit`78 containing fuel lters 79 and 80, a vari- `able area orifice 81, a fuel pressure responsive spring loaded valve 82 and ya spring loaded check Valve 83. A

meteringvalve 84 operatively connected to orice 81 is spring'load applied thereto, regulates the pressure of the fuel downstream therefrom at a predetermined constant value Pr. Fuel flows from chamber 88 to chamber 89 via a fixed area restriction 92 lixedly secured in pis-ton 87 andthen flows to the interior of casing 77 at drain Ipres-l sure Pu via a passage 93. The flow through passage 93 and thus the pressure drop across piston 87 is controlled by a variable area orice 94 which is operatively connected tothe discharge end of passage 93. It will -be noted Y that the piston S7 has a relatively large area exposed to the lower fuel pressure in chamber 89 derived from pressure Pr such that piston 87 is stabilized when the inverse `ratio of fuel-pressures thereacross equals the area ratio of piston 87 and .is moving Whensaid ratio of pressures is upset. An 'adjustable maximum ow stop 95 threadedly engaged with casing 77 is `adapted t0 engage piston 87 y thereby limiting movement of metering valve 84 in an opening direction. An adjustable minimum flow stop which includes a threaded member 96 threadedly engaged With casing 77 and -a lever member 97 pivotally secured to casing 77 and member 96 is `adapted to engage end portion 86 thereby limiting movement of metering valve 84 in aclosing direction.

The position of metering valve 84 and thus fuel ow through conduit 44 to the engine is regulated as a function of the speed N2 of high pressure air compressor 32 by a governor land acceleration cam having separate eirp a restriction 126 xedly secured in piston 109 to chamber cumferential portions 98 and 99 which are contoured radially as predetermined functions of high pressure air compressor speed N2 to provide corresponding governing and acceleration fuel ows, respectively. The cam portion 99 is contoured axially as a function of compressor inlet -air temperature T1 to providel temperaturev compensation for acceleration fuel flow.

A second cam xedly secured to cam portions 98 and 99 is provided with separate circumferential portions 100 .and 101 which are contoured radially as predetermined func-tion of high pressure air compressor speed N2.

The governor and acceleration cam and second cam secured thereto are slidably mounted for axial movement on a shaft 102 and are rotatable with shaft 102 which is journalled at one end in casing 77 and which is provided with an integral pinion 103 at the opposite end. The pinion 103 is engaged by a rack 104 xedly secured to a servo piston 105 which serves to rotate pinion 103 and shaft 102 as a function of high pressure compressor speed NZ in response to movement of piston 105.V A cam follower 106 is urged into engagement with portion 99 of the governor and acceleration cam by a lever 107 pivotally connected at one end to the cam follower 106 and at the opposite end pivotally connected to a reduced diameter extension 108 of a servo piston 109. A spring 110 suitably interposed between lever 107 and casing 77 serves to bias the lever 107 to effect engagement of follower 106 with cam portion 99 when the lever 107 is biased out of 'engagement with an adjustable fulcrum or abutment member 111 by servo piston 109 as shown .in FIGURE 2. The fulcrum or abutment member 111 is adjustably secured to casing 77 by a screw 112 threadedly engaged therewith. A cam follower 113 is urged into engagement with cam portion 98 by a lever 114 pivotally connected at one end to follower 113. A tension spring 115 connected to casing 77 and lever 114 serves to load lever 114 in a counterclockwise direction. The opposite endof lever 114 is adapted to engage a ball servo valve 116 which cooperates with a valveseat 117 formed at the discharge end of a passage 118 defined by an annular extension 119 integral with servo piston 109 which annular extension extends through an opening 120 in casing 77. An adjustable fixed stop 121 threadedly engaged with casing 77 is enagageable with lever 114 to thereby limit movement of the same. The reduced diameter section 108 extends from the opposite side of servo piston 109 through an opening 122 in casing 77. The servo piston 109 is slidably carried in a chamber 123 and arranged to engage a stop 124 which engagement permits the lever 107 to occupy a slight spaced relationship relative toadjustable vfulcrum 111 when the follower 106 occupies a position corresponding to the maximum depression of contouredl portion 99. Fuel at constant regulated servo pressure Pr is supplied to chamber 123 via a passage 125 leading from conduit 90 and flows through 123 on the opposite side of piston 109 from which it flows through passage 118 to the interior of casing 77 at drain pressure P0. The -fuel pressure PS in chamber 123 on the downstream side of restriction 126 is controlled by the ball valve 116. The larger and smaller elfective areas of piston 109 exposed to fuel pressures Ps and Pr,

respectively, have a predetermined fixed area ratio which requires that a corresponding ratio of pressures Ps and l"r be established to stabilize piston 109 at any position "in its range of travel. The piston 109 will respond to a variation from the predetermined pressure ratio 'Pr/PS and continue to move until the fuel pressure Ps is regu- Y lated by the action of ball valve 116 to the value required to establish the predetermined ratio Pr/Ps. It Will-be noted that the servo piston 109 is of the follow-up type which means that, depending upon the direction of movement of ball valve 116 relative to valve seat 117, the piston 109 -will move inthe same direction in response to the change in pressure PS until the position of valve seat 117 relative to ball valve 116 is such that the pressure Ps required to stabilize piston 109 is again re-established. For additional details of the governor and acceleration cam and associated linkage mechanism described above, reference is made to U.S. Patent No. 3,138,926 issued June 30, 1964, in the name of H. L. McCombs, Ir. (common assignee). The position of the ball valve 116 for a fixed position of follower 113 is dependent upon the position of a spring loaded follower 127 vattached to lever 114 through a rod 128, a bell crank 129 pivotally secured at one arm to rod 128 and pivotally secured to casing 77 at its rnidsection, a follower 130 slidably engaged with the other arm of bell crank 129 and pivotally connected to a rod 131 which, in turn, is pivotally connected to lever 114. The follower 127 is responsive to the position of a speed request cam 132 slidably mounted on a shaft 133 and rotatable therewith in response to movement of throttle lever 54. Throttle lever 54 is xedly secured to a gear 134 which meshes with a gear 135 xedly secured to the shaft 133. An engine idle speed adjustment includes an adjustable fixed stop 136 pivotally secured to casing 77 and at one end pivotally secured to a rod 137 threadedly engaged with casing 77. The stop 136 is adapted to engage a ange 138 iixedly secured to rod 131 to thereby limit movement of the same in a corresponding direction. The movement of rod 131 in the opposite direction is limited by a stop member 139 which engages a Iflange 140 lixedly secured to rod 131. The stop member 139 is pivotally secured to casing 77 and provided with an farm 141 which is biased against an adjustable fixed stop 142 threadedly engaged with casing 77 by a rod 143 integral with a piston 144. The piston 144 is slidably carried in a chamber 145 and is biased away from arm 141 by a spr-ing 146 interposed between casing 77 and piston 144 and drain fuel pressure Po acting against one side of piston 144. The rod 143 is biased against arm 141 by constant regulated fuel pressure Pr which communicates with chamber 145 at the opposite side of piston 144 via a passage 148 leading to conduit 90. The passage 148 is vented to drain fuel pressure Po via a restriction 149. A normally closed valve 150 in passage 148 is actuated by an electrical solenoid 151 which is energized at a predetermined throttle lever 54 positioned by a switch 152. A cam 153 rotatable with throttle lever 54 serves to activate switch 152 at the predetermined throttle lever position. With valve 150 closed, the fuel at pressure Pr in chamber 147 is permitted to drain to the interior of casing 77 at pressure Po via restriction 149.

The servo piston 105 which actuates rack 104 is slidably carried in a chamber 154 which receives fuel rat constant regulated servo pressure Pr via passage 125 vented thereto. Fuel ows through a restriction 155 ixedly secured in piston 105 to chamber 154 at the opposite side of piston 105 from which the fuel ows through a passage 156 having a variable area valve 157 at the discharge end thereof to the interior of casing 77 at drain pressure P0. The effective ilow area of valve 157 -is controlled as a function of high pressure compressor speed N2 by a lever 158 pivotally secured t-o casing 77 and engageable at one end with a bearing member 159 slidably carried on a rod 160 which, in turn, is integral with a rotatable support 161. The support 161 is provided with a shaft 162 having a gear 163 integral thereto which is driven by the high pressure compressor 32 via gearing and shafting 51. A pair of centrifugal weights 164 pivotally secured to support 161 extends into engagement with the bearing member 159 to thereby load the same axially in response to the centrifugal force derived from the rotation of the weights 164. The force applied -to lever 158 by bean'ng member 159 is opposed by a constant reference force derived from a spring 165 which is applied to lever 158 through -a plate 166 and roller 167 which contacts plate 166 and lever 158 and rolls therebetween. The opposite end of spring 165 is engaged by a spring opposite end is pivotally secured t-o a follower 173 which bears against contoured portion 100. A tension spring 174 connected to casing 77 and lever 172 serves to load the lever 172 in a clockwise direction.

The governor and acceleration cam `and second cam secured thereto are actuated axially on shaft 102 as a function of compressor inlet air temperature T1 by a piston 175 integral with a rack 176 which is provided with a retaining annulus 177. One end -of a lever 178 pivotally y secured to casing 77 is retained by annulus 177 and the opposite end of lever 178 is retained by a retaining annulus 179 formed on the second cam. The piston 175 slides in a chamber 180 -to which fuel at regulated servo A pressure Pr is -supplied via a passage 181. Fuel ows through a restriction 182 fixedly secured in piston 175 to chamber 180 at the opposite side of piston 175 from j which the fuel flows to the interior of casing 77 at drain pressure Po via a passage 183 having a variable area valve 184 at the discharge end thereof. The eifective flow area of passage 183 and thus fuel pressure Ps in chamber 180 is varied by valve 184 in response to movement of a lever 185 pivotally connected at one end to rack 176. The opposite end of lever 185 is engaged by f an arm 186 pivotally secured to casing 77 The arm 186 is actuated by a roller 187 which rides against a beveled surface 188 formed on a cylindrical member 189 slidably carried by casing 77 and lixedly secured to a movable end l `of a bellows 190 which is filled with a fluid which expands and contracts axially in response to compressor inlet tern- Vperature T1 sensed by yunit 50. The roller 187 is rota- V. tably secured to a yoke 191 which is pivotally secured to one end of a bell crank 192. The bell crank 192 is pivotally secured to casing 77 and is pivotally secured at, its opposite end to the movable end of a bellows 193 which expands and contracts axially in response to the temperature sense-d by a liquid iilled tube 194 connected between bellows 193 and temperature unit 50. The tube 'Y 194 and a similar tube portion 195 connected between temperature unit and bellows 190 are responsive to the same ambient temperature. However, it is desired to compensate for the effect of the ambient temperature on tube portion 195 such that output motion of arm 186 is a function of ycompressor inlet Temperature Ti only. To this end, the elfect of tube 194 which responds to the ambient temperature and not to compressor inlet temperature Ti serves to compensate for the elfect on tube 195 as will be -described hereinafter. A preload .against bellows 193- is maintained by a spring 196. A spring 197 interposed between casing 77 and arm 186 serves to lbias arm 186 against roller 187.

The cam follower 106 which engages contoured portion 99 of the second cam is pivotally secured to a yoke 198 which rotatably carries a roller 199. The roller 199 rolls between one arm of a lever 200 and cross arm 'Y 201 of a T -shaped lever 202 which is pivotally secured to casing 77. The opposite end of the T-shaped lever 202 is pivotally secured to the movable end of a bellows 203 which is adjustably secured to casing 77 at its opposite xed end by a threaded extension 204 threadedly engaged with casing 77. The bellows 203 responds to compressor discharge pressure Pc which is fed to a chamber The load applied to lever 200 lthrough roller 199 is opposed by a constant reference force derived from a spring 207 interposed between a plate 208 and a spring retainer 209, M the latter being supported by discs 210 which, in turn,. are supported by a fixe-d support member 211 threadedly 205 surrounding bellows 203 Via .a passage 206.

. arm 232 xedly secured to piston 105.

- inlet air pressure Pi. secured together and are slidably carried on a shaft 235 secured to casing 77. The discs 210 provide for temperature compensation of the fuel surrounding spring 207. The force of spring 207 is transmitted to lever 200 through roller 199' which rolls between plate 208 and the adjacent arm of lever 200 and which is rotatably carried Aou a yoke 212 pivotally secured to end portion 86 of metering valve 84.

A compressor pressure limiting device generally indicated by numeral 213 serves to limit the compressor Vdischarge pressure Pc to a predetermined maximum value.

lThe pressure limiting device 213 includes a bellows 214 vented interiorly to passage 206 upstream from a restriction 215 via a restriction 216 and exposed exteriorly to atmospheric air pressure Pa in a chamber 217. The bellows 214 is loaded in compression by a spring 218 which bears against a spring retainer 219 xedly secured to the closed end of bellows 214. A lever 220 pivotally secured at one end to casing 77 isV pivotally secured to spring retainer 219 such that expansion or contraction of bellows 214 results in pivotal movement of lever 220 about its one end. The opposite end of lever 220 is adapted to engage the discharge end of a passage 221 leading from passage 206 downstream from restriction 215 to chamber 217 at atmospheric air pressure Pa.

Fuel at regulated servo pressure Pr is delivered to the afterburner fuel control 55 at a predetermined high pressure air compressor speed N2 via a passage 226 connected to passage 181, a slide valve 227, and a passage 228.

. lever 230 -is actuated by arm 232 ,causing slide valve 227 to move upward against spring 229 thereby communicating passage 226 with passage 228 to permit fuel at regulated servo pressure 1:'r to ow to the afterburner fuel control 55.

The speed request cam 132 is actuated axially on shaft 133 as a function of compressor inelt air temperature Ti and pressure P1 by either of two cams 233 or 234 which are contoured radially as a function of compressor inlet air temperature T1 and axially as a function of compressor The cams 233 and 234 are tixedly having a pinion 236 xedly securedy thereto which meshes with rack 176. The cams 233 and 234 rotate with shaft 235 and are translated on shaft 235 by a follower 237 pivotally secured to casing 77 and provided with an end portion which extends into an annularrecess 238 separating cams 233 and 234. The opposite end portion of follower 237 extends into an annular recess 239 formed in a piston member 240 slidably carried in a chamber 241. Fuel at regulated servo pressure P1P is conducted via a passage 242 from passage 181 to chamber 241 at one side of pistou 240 from which the fuel ows through a restriction 243 xedly secured to piston 240 to chamber 241 at the opposite side of piston 240 from which the fuel flows to the interior of casing 77 at drain pressure Po i via a passage 244 having a variable area valve 245 at the discharge end thereof. The effective ow area of valve l 245 and thus the pressure drop across piston `240 is controlled by a lever 246 pivotally secured to casing 77 and provided with an end portion which extends into `a chamber 247 and which is pivotally secured to the movable end of a sealed bellows 248. A fixed end of the bellows 248 is adjustably anchored to casing 77 by screw member 249 threadedly engaged with casing 77 The bellows 248 expands or contracts in response to a decrease or increase,

respectively, of compressor inlet air pressure P1 which is 'supplied to chamber 247 via a passage 250. The force 4applied to lever 246 by bellows 248 is opposed by a constant reference force derived from a spring 251 and transmitted to lever 246 through a roller 252 which rides between a plate 253 against which spring 251 bears and an arm 254 integral with lever 246. The roller 438 is rotatably carried by ayoke 255 which is pivotally secured to piston 240. A spring retainer 256 supported by temperature responsive discs 257 serves to retain the one end of spring 251.

The cam 132 is actuated axially by a lever 258 having an end portion which extends into an annular recess 259 formed at one end of cam 132. The lever 258 is Aintegral with a casing 260 having a chamber 261 in which a piston 262 is slidable. The casing 260 is pivotally supported on casing 77 by a cylindrical extension 263 integral with casing 260 and pivotally secured in a bore 264 in casing 77 and is provided with integral parallel arms 265 and 266. Arm 265 is loaded by a spring 266 which urges casing 260 counterclockwise. Lever 268 is pivotally secured to arm 266 and the lever and arm are provided with cam followers 269 and 270, respectively, secured thereto which are adapted to engage cams 233 and 234, respectively. As shown in FIGURE 2, the cam follower 270 is held away from cam 234 when cam follower 269 is engaged with cam 233. However, under certain conditions of operation the cam follower 269 is held away from cam 233 and cam follower 270 is permitted to engage cam 234. In either event, it will be understood that only one of the cams 233 and 234 is effective at any given time depending upon which of the followers 269 and 270 is engaged with its respective cam surface. To this end, the lever 268 is attached at one end to one end of a tension spring 271 which is attached at the opposite end to arm 265. A roller 272 rotatably carried by a yoke 273 is engageable with opposing surfaces of arm 265 and lever 268. The yoke 273 is pivotally secured to piston 262.

A spring 274 interposed between piston 262 and casing 260 opposes regulated servo pressure Plr which is transmitted to chamber 261 via a passage 275 leading to the bore 264, a central passage 276 in extension 263 and a by the spring bearing thereagainst whereby passage 278 is vented to drain fuel pressure Po. A lever 281 iixedly secured to shaft 133 engages slide valve 279 at a fuel cutoi position of throttle lever 54 and actuates valve 279 to thereby establish communication between passages 278 and `280 and permit fuel at pressure P1 to flow to the back side of valve 279. The spring force acting against valve 82 assisted by fuel pressure P1 overcomes the fuel pressure P2 acting against the opposite side of valve 82 thereby actuating valve 82 to a closed position which results in shutting off the fuel flow to conduit 44.

The fuel pressure drop P1P2 across metering valve 84 is maintained at a predetermined value bya by-pass valve 282 which controls the effective flow area of a fuel by-pass conduit 283 leading from passage 78 to the drain passage 53. A piston 284 integral with by-pass valve 282 is lslidable within a chamber 285 and is exposed on one side to fuel pressure P2 which is supplied to chamber 285 via a passage 286 having a restriction 287 therein. The opposite side of piston 284 is exposed to servo fuel pressure Ps derived from fuel pressure P1 and supplied to chamber 285 via a passage 288, a chamber 289, and a passage 290. Y The servo fuel pressure 1:s is controlled by a valve 291v connected to the inlet end of passage 290 and arranged to vary the effective flow area thereof in response to movement of a lever 292 pivotally connected to casing 77. Lever 292 is pivotally connected to and actuated by the closed end of a bellows 293 which is exposed on one side to fuel pressure P1 in chamber 289 and on the opposite side to fuel pressure P2 in a chamber 294 which communicates with chamber 285 via a passage 295. A predetermined spring load is imposed on bellows 293 by a spring 296 supported by temperature responsive discs 297 and adjustable retainer 298 threadedly secured to casing 77. A spring 299 interposed between casing 77 and piston 284 loads the by-pass valve 282 in a closing direction. A spring 300 interposed between piston 284 and a piston 301 slidably carried by valve 282 loads the piston 284 in opposition to spring 299. The load derived from spring 300 varies depending upon the position of piston 301 which responds to the fuel pressure differential P1-P2 thereacross. A restricted passage 302 communicates passage 290 with passage 78 at fuel pressure P2. It will be noted the piston 301 coacts with the valve 282 such that the effective ow area of valve 282 depends upon the position of piston 301 as well as the position of valve 282. For further details of structure and operation of the bypass valve 282, reference is made to copending application Serial No. 782,948, filed December 24, 1958, in the name of F. R. Rogers et al. (common assignee).

An emergency fuel schedule is supplied to conduit 44 in the event of a mulfunction of the above ydescribed structure of the main fuel control 43. To this end, a spring loaded fuel transfer valve 303 slidably carried in casing 77 is arranged to divert fuel from passage 78 upstream from filter 79 to a conduit 304 leading to passage 44 and provided with a variable area valve 305 which controls the effective flow area thereof. The valve 305 is pivotally connected to a lever 306 which, in turn, is fixedly secured to and rotated by a gear 307 which meshes with gear 134 and is positioned as a function of throttle lever 54 position. The fuel pressure differential across valve 305 is .regulated by a double ported by-pass valve 308 which controls fuel ow through a fuel by-pass conduit 309 leading from conduit 304 to the conduit 283 at drain pressure Po. A diaphragm 310 xedly secured to valve 308 and loaded by a spring 311 supported by adjustable retainer 312 threadedly engaged with casing 77 is responsive to fuel pressure P1 upstream from valve 305 and a servo fuel pressurePs derived from fuel pressure P1 and regulated by a Valve 313 upstream from a fixed area restriction 314. The valve 313 and restriction 314-are arranged in series in a conduit 315 leading from conduit 309 to conduit 304. The fuel pressure Ps intermediate valve 313 and restriction 314 varies as a function of the area ratio of valve 313 and restriction 314 which area ratio depends upon the position of valve 313. The valve 313 is slidably carried in casing 77 and is actuated by one end of a lever 316 pivotally secured to casing 77.

The oppositeend of lever 316 is pivotally connected tothe movable end of a sealed bellows 317 which is anchored at its opposite end to casing 77 by an adjustable retaining member 318 t-hrea'dedly engaged with casing 77. Compressor inlet air pressure P1 is supplied via a passage 319 leading from passage 49 to a chamber 320 surrounding bellows 317 which expands and contracts in response to a decrease and increase, respectively, in pressure P1. The transfer valve 303 is held in the position shown in FIGURE 2 by a spring 321 which is assisted by fuel pressure P1 in a chamber 322 containing spring 321. The chamber 322 receives fuel from conduit 78 via a restricted passage 323 in one end of valve 303 and is vented to bypass conduit 309 at drain pressure Po via a passage 324 containing a normally close-d valve 325 which is actuated by an electrical solenoid 326. The opposite end of valve 303 is exposed to fuel pressure P1 in a chamber 18 which communicates with conduit 78 Via a passage 19 formed in valve 303. The solenoid 326 is energized by switching means which may be manually actuated or automatically actuated in response to a malfunction of the main control system heretofore described. Energization of the solenoid 326 causes valve 325 to open whereupon the fuel pressure in chamber 322 decreases to drain pressure Po by virtue of the pressure drop across restricted passage 323 which allows fuel pressure P1 acting against the one en-d of valve 303 to overcome spring 321 thereby displacing valve 303 to the right to cut olf flow through conduit 78 and simultaneously'divert ow from conduit 78 to conduit 304. A spring loaded check valve 327 in conduit 304 is held closed by fuel pressure P2 downstream therefrom during normal operation. Under emergency operation the che-ck valve 327 is open and the check valve j 83 in conduit 78 is held closed `by the fuel pressure downstream therefrom.

Referring to FIGURES 4, 4a and 5, numerals 328 and 329 designate casings of the afterburner fuel control 55 and exhaust nozzle control 70, respectively. A passage 330 vents the interior of casing 328 to the interior of casing 329 which, in turn, is Vented to conduit 53 at drain pressure Po via passage 63.

Referring to FIGURES 4 and 4a, the centrifugal pump 60 is arranged to discharge into a conduit 331 which contains a check valve 332 and a pressure regulating valve 333 and which leads to the inlet of a metering valve 334 from which fuel iiows through a throttling valve 335 to a conduit 336 leading to conduit 56 which, in turn, supplies fuel to afterburner manifold 38. A pressure regulated valve 337 and fuel cut-off Valve 338 are arranged in series flow relationship in conduit 336. The remaining two afterburner manifolds 39 and 40 are supplied fuel via separate conduits 339 and 340, respectively, leading from Conduit 331 to valve structure, not shown, identical to metering valve 334, throttling valve 335, pressure regulating valve 337 and cut-olf valve 338 and designate-d by boxes 341 and 342, respectively, which communi-cate with outlet conduits 57 and 58 leading to afterburner manifolds 39 and 40, respectively.

A pressure actuated valve 345 in conduit 59 leading to the inlet of pump 60 is actuated to an open position by regulated fuel pressure Pr which is supplied thereto via a passage 346 leading from the main lfuel control 43 to the exhaust nozzle control 70, a passage 347 in casing 329, a passage 348 connecting passage 347 with casing 328, a passage 348 leading to the inlet of a valve 349 from which the fuel at regulated pressure Pr ows via passage 350 to valve 345. The valve 349 is provided with an integral piston 351 having an annular area at one end exposed to passage 348 at regulated pressure Pr and an opposite end exposed to fuel pressure in a chamber 352. The chamber 352 is vented to regulated fuel pressure P, via a passage 353 leading from passage 348 and to drain fuel pressure Po via a pas-sage 354 leading to the interior of casing 328 at pressure P0. As shown in FIGURE 4, the piston 351 is biased against a stop 355 integral with casing 328 by regulated pressure Pr in oppositi-on to the force of a spring 356 interposed between stop 355 and piston 351. Aapper valve 357 engageable with orifices 358 and 359 in series flow with passages 353 and 354, respectively, is attached to one end of a lever 360 which is pivotally Isecured to casing 328 and which is pivotally secured at its opposite end to a stem 361 ixedly secured to a diaphragm 362. The diaphragm 362 is loaded by a spring 363 and is vented on one side to conduit 331 upstream of check valve 333 via passage 364 and on the opposite side to conduit 331 downstream of check valve The centrifugal pump 60 is a relatively high capacity Y pump and does not therefore function efficiently at rela- 4tively low flow rates.

The initial low fuel flow rate for afterburner operation is supplied by the engine driven positive displacement type pump 76 which also supplies pressurized fuel to the exhaust nozzle control 70 (FIG- URE 5). To this end, fuel is supplied to conduit 331 from the pump 76' viaa conduit 368 containing a lter 369 and a spring loaded pressure regulating valve 370 (FIGURE 5), a passage 371 leading to the inlet of a valve 372 from which fuel flows through a passage 373 to conduit 331 upstream from check valve 333. The

Ipressure regulating valve 370 functions to reduce the relatively high pressure fuel which may be on the order 3,000 `p.s.i. discharged =by pump 7 6 to a lower pressure such as 1,000 p.s.i. which is supplied` to conduit 371. The valve 372 has smaller area portion 374 exposed to the fuel pressure in passage 371, and is provided with a piston portion having an annular portion 375 which is exposed to drain fuel pressure P0 via a passage 376, and a larger area portion 377 exposed to the fuel pressure in conduit 331 upstream from check valve 332 via a passage 378.

The variable area metering valve 334 in flow controlling relationship with conduits 331 and 336 is provided with a piston portion 379 which is slidably carried by casing 328 and which separates variable volume chambers 380 and 381. Filtered fuel is supplied to chamber 380 from conduit 331 via a passage 382 containing a filter 383. A branch passage 384 containing a restriction 385 communicates passage 382 with chamber 381. The metering valve 334 is positioned in accordance with the servo pressure Px in chamber 381 which is controlled by a servo valve 386 which coacts with the inlet end of an axial passage 387 formed in valve 334 to vary the ow out of chamber 381. A spring 388 interposed between piston portion 379 and casing 328 and a spring 389 interposed between servo valve 386 and piston por- Ition 379 provide oppositely acting preloads on valve 334.

The servo valve 334 is positioned toward or away from passage 387 by a lever 390 pivotally secured at one end to an extension 391 of valve 334 whichextension is slidably carried by casing 328. An adjustable stop 392 threadedly engaged with lever 390- is adapted to engage casing 328, thereby limiting move-ment of lever 390. The lever 390 is xedly secured to a shaft 393 which is journalled in casing 328 and which slidably carries a follower 394 having a flange 395 formed thereon. A rod 396 iixedly secured to lever 390 is slidably carried in a slot 397 in iange 395 to thereby permit follower 394 to move axially relative to lever 390 but prevent relative rotational movement therebetween. The follower 394 is provided with an adjustable arm 398 threadedlyengaged therewith and adapted to engage a cam or ramp member 399 pivotally secured to casing 328 by means of a -shaft 400. with cam member 399 rides against a three dimensional cam 402 xedly secured to a shaft 403 suitably supported by casing 328 for rotational and axial movement.

l The shaft 403 is translated by a lever 404 pivotally secured to casing 328 and extending into engagement with a retaining annulus 405 formed -on shaft 403. The opposite end portion of lever 404 is pivotally secured tol a servo piston 406 which responds to a variable servo fuel pressure diiferential PS-Pr thereacross. The fuel pressure lFS-Pr is cont-rolled by a servo valve 407 which regulates the :fuel pressure l?s Aand which is connected to one end of a lever 408 pivotally secured to casing 328.- The lever 408 is actuated by a bel-lows 409 having one end anchored to casing 328 and an opposite closed end which bears against one end of lever 408. A spring 410 urges lever 408 into engagement with'the closed end of bellows 409. A tube 411 filled with a temperature responsive liquid is connected at one end to temperature probe 61 and at an `opposite end to -the interior of bellows 409 which, like tube 411, is filled with temperature responsive liquid. The bellows 409 expands or contracts by virtue of the volume expansion or contraction of A follower 401 threadedly engaged i" the temperature responsive liquid in response to temperature variations at probe 61. The shaft 403 is rotated by a rack 412 (see FIGURE 5) which engages la pinion 413 xedly secured to shaft 403 and which forms part of the control mechanism of the exhaust nozzle control 70 to be described. It will be understood that the shaft 403 is translated as a function of compressor inlet ternperature Ti and rotated by rack 412 as a function of exhaust nozzle area, pressure ratio Ffm/PTF, across turbines 33 and 30 and the position of throttle lever 54.

The follower 394 is translated on shaft 393 by a lever 414 pivotally secured to casing 328 and engageable at one end with a flange 395 integral with follower 394. A spring 415 interposed between lever 390 .and follower 394 serves to bias ange 395 into engagement with the adjacent end of lever 414. The remaining two followers 394 connected to valve structure 341 and 342, respectively, likewise are provided with similar structure as shown in FIGURE 4a where the followers 394 simultaneously respond axially to movement of lewer 414 and rotate independently of each other to position the respective control levers 390 to a variable degreev depending upon the contour of the respective cams 402, 451 and 452. The opposite end yof lever 414 extends into engagement with a retaining annulus 416 formed in an extension of a servo piston 417 slidably carried in casing 328 and responsive to a fuel servo pressure differential Ps--Pr thereacross. The pressure dierential Ps-Pr is controlled by a servo valve 418 which regulates fuel pressure Ps in response to movement of a lever 419 pivotally secured to casing 328. The lever 419 is actuated by a bellows 420 which is anchored at one end to casing 328 and vented interiorly to compressor discharge pressure Pc via passage 62. An evacuated bellows 421 is xedly secured at one end to casing 328 and at its opposite end is iixedly secured to bellows 420 which, in effect, renders the output force of bellows 420 a function of compressor discharge pressure Pc absolute. A feedback torque is applied through lever 419 in opposition to the torque derived from bellows 420 through a roller 422 which rides between lever 419 and a plate 423 loaded by .a constant reference force derived from la spring 424. One end of spring 424 is supported by temperature responsive discs 425 and adjustable retaining member 426 threadedly engaged with casing 328. The roller 422 is rotatably secured to a yoke 427 pivotally secured to servo piston 417 and is positioned simultaneously with movement of servo piston 417 to vary the effective lever arm of lever 419 through which the constant reference force spring 424 Iacts to thereby balance the opposing torque derived from bellows 420. The temperature responsive discs provide temperature compensation with regard to the fuel surrounding spring 424.

The fuel pressure differential P1-P2 across metering valve 334 is controlled at a predetermined constant value by throttling valve 335 in series with and downstream from metering valve 334. A piston 429 integral to valve 335 is provided with a relatively large face 430 against which a servo fuel pressure PX acts, an intermediate face 431 to which fuel at pressure P1 is supplied via a passage 432 leading from passage 382, and a relatively small face 433 which further includes Iannular end portion 434 against which fuel at pressure P2 acts. The servo fuel pressure Px is generated between a restricted inlet passage 435 leading from passage 382 and a discharge passage 436 having la variable area valve 437 arranged in the discharge end thereof. The How out of passage 436 and thus pressure 1:'X is controlled by valve 437 which is connected to the movable end of a bellows 438 exposed on one side to fuel pressure P1 via a passage 439 leading from the upstream side of metering valve 334 and exposed on the opposite side to fuel pressure P2 via a passage 440 leading from the downstream side of metering valve 334. The fuel pressure differential Pl-PZ acting across bellows 438 is opposed by a spring aasaso i3 441 interposed between an adjustable lspring retainer 442 threadedly secured to casing 328 and a sp-ring retaining member 443 xedly secured to the movable end of -bellows 438. The bellows 438 is anchored at its open end to casing 328 by Iany suitable means providing a uid seal.

The cut-olf valve 338 is responsive to metered fuel pressure P3 is conduit 336 .and to a spring 444 and fuel pressure in a chamber 445 which receives fuel from conduit 336 via a passage 446 in paral-lel with check valve 337 and restricted passages 447 and 448. A discharge passage 449 conducts fuel out of chamber 445 and the iiow therethrough is controlled by a valve in the exhaust nozzle control 70 to be des-cribed. A filter 450 disposed in passage 446 serves to filter the fuel received by passages 447 and 448.

As pointed out heretofore, the afterburner fuel control 55 controls the iiow of fuel to three afterburner fuel manifolds 38, 39 and 40. The above described metering valve 334, throttling valve 335, cut-off valve 338, pressure regulating valve 337 Iare duplicated for each of the other two manifolds 39 and 40 and designated by boxes 341 and 342, respectively. The operation of the metering valve 334 in the boxes 341 and 342 is controlled by cams 451 and 452, respectively, which, like cam 402, are carried by shaft 403 and rotated and translated as a function of compressor inlet temperature Ti and exhaust nozzle area, pressure ratio PIM/Ffm across turbines 33 and 30, and throttle lever 54 position, respectively. As in the case of cam 402, cams 451 and 452 each Iactuate a fol-lower 401 connected to a cam member 399 pivotally secured to casing 328. The cam member 399 in each case actuates a follower 394 which, in turn, rotates a lever 390 fixedly secured to lan associated shaft mounted for rotation in casing 328 which lever 390 is connected to control the operation of its associated metering valve 334.

Now, referring to FIGURES 5 and 6, which together illustrate the exhaust nozzle control 70 in more detail, the conduit 368 is connected to a passage 453 leading to the inlet of a spool valve 454 which is shown in a null position whereby lands 455 and 456 thereof block passages 457 and 458, respectively, which lead to passages 66 and 68 communicating with piston 65. Movement of spool valve 454 in one direction from the null position shown serves to simultaneously communicate passage 457 with passage 453 and communicate passage 458 with drain fuel pressure Po via drain passage 459 leading to fuel conduit 76, whereas movement in the opposite Adirection communicates passage 458 with passage 453 and communicates passage 457 with drain fuel pressure Po via drain passage 460 leading to drain passage 459. A servo piston 461 integral with spool valve 454 is provided with an extended portion having a passage 462 therein which is in series with a passage 463 leading from one side of servo piston 461. The opposite side of servo piston 461 communicates with regulated fuel pressure in passage 371 via a passage 464. A sprin-g loaded check valve 465 communicates passage 371 with drain passage 459 :and opens when the pressure of the fuel in passage 371 exceeds a predetermined value. A restricted passage 466 permits fuel to flow from pas-sage 464 to passage 463. A solenoid operated valve 467 disposed in passage 463 is biased to a closed position in response to energization of the solev noid 467 attached thereto to thereby prevent flow through passage 463. With valve 467 in an open position the fuel press-ure on one side of piston 461 is controlled by a valve member 470 which coacts with the discharge end of passage 462 to vary the effective ow area thereof. The va-lve 470 is attached to one end of 4a lever 471 which, in turn, is pivotally secured to lone end of a rod 472 and actuated by a follower 473 lixedly, secured thereto. The follower 473 rides against a first contoured portion f a three dimensional nozzle area and fuel liow correlation cam 474 fixed-ly secured toa shaft 475 mounted on casing 329 for rotational `and axial movement relative thereto. The |shaft 475 is rotated as a function of exhaust nozzle area by pulley 74 through gears generally indicated by 476. The shaft 475 is tnans'lated as -a function of the pressure ratio Pim/PTF, across turbines 33 and 30 by a lever 477 pivotally connected at one end to shaft 475 and pivotally connected to an extension 478 integral with a servo piston 479. Fuel at regulated servo pressure Pr is supplied to one side of piston 47 9 at a predetermined high pressure compressor speed N2 from main fuel control 43 via a passage 480, a spring loaded spool valve 481 actuated by a first contou-red portion of a cam 482, a passage 483, -a two-position spool valve 484, and passage 228. The piston 479 is pnovided with a restriction 486 which communicates the one side of piston 479 with the opposite side thereof from 4which opposite side the fuel escapes to the interior of casing 329 at drain pressure Po via discharge passage 487. The pressure drop across the piston 479 is controlled by a servo valve 488 secured to one end -of -a lever 489 pivotally secured to -a stem 490 which is fixedly secured `at one end to the movable end of an evacuated bellows 491 and which is iixedly secured at the opposite end to the movable closed end of a bellows 492. The evacuated bellows 491 is anchored at one end to casing 329. The bellows 492 is anchored at one end to casing 329 and is vented interiorly to pressure Pm upstream of turbine 33 via passage 72. The lever 489 is pivotally -secured to casing 329 at 494. A roller 495 rides against lever 489 and across an arm integral with a lever 496 which is pivotal-ly secured to casing 329 and a stem 497. The stem 497 is lixedly secured at one end to the movable end of an evacuated bellows 498 and at its opposite end to the movable closed end of a bellows 499. The evacuated bellows 498 is anchored at one end to casing 329. The bellows 499 is anchored at one end to casing 329 and is vented interiorly to pressure PTF, downstream of turbines 30 via passage 73. 'Ihe roller 495- is rotatably carried by a yoke 501 pivotally secured to a spring loaded follower 502 which is slidably carried by casing 329 and which is biased into engagement with the first contoured surface of the three dimensional cam 482. The cam 482 is mounted on a shaft 503 which rotates the cam 482 :and which is provided with an integral pinion S04. A rack 505 tixedly secured to a servo piston 506 drives the pinion 504 .in response to movement of piston 506. The cam 482 is slidably mounted for axial movement `on shaft 503 and is translated |by a yoke 507 fixedly secured to extension 478 and suitably secured to an annulus on the cam 482 to penmit rotational movement thereof. Fuel at regu-lated pressure Pr is conducted to one side of piston 506 via a passage 508 leading from passage 483. Fuel is transmitted through a restriction 509 in piston 506 to the opposite side of piston 506 from which fuel flows through a passage 510 to the main fuel control 43 (FIGURE 2). Referring to FIGURE 2, the passage 510 discharges into a chamber 511 which is vented to the interior of casing 77 at drain pressure Po via a passage 512. A valve 513 connected to the discharge end of passage 510 serves to control the effective iiow area thereof and thus servo pressure PX on the one side of piston 506. A lever 514 pivotally secured to casing 77 is actuated by the movable end of a bellows 515 having a xed end anchored to casing 77. A restriction 516 fixedly secured to the movable end of bellows 515 permits fuel to ow out of bellows 515 to chamber 511 at drain pressure P0. A roller 517 rides between lever 514 and .a plate 518 which is loaded by a constant reference Iforce derived from a sp-ring 519 having a fixed end supported by an adjustable retainer 520 threadedly engaged lwith casing 77. The roller 517 is rotatably connected to a yoke 521 which is pivotally secured to a follower 522 slidab-ly carried by casing 77 and eng-ageable with cam portion 101. The interior of bellows 515 is vented to the interior tof a bellows 523 in'exhaust nozzle contr-ol 70 (FIGURE 6) via a passage 524. Referring to FIGURE 6, restricted passage 525 communicates fuel at regulated pressure lr to passage 524 from passage 483. The fuel flow out of passage 524 and thus fuel pressure Ps within bellows 51S is controlled by .a servo valve 526 xedly secured to the movable end of 'bellows 523 which coacts with the inlet end of a tubular member 527 ixedly secured to a xed end of bellows 523 and communicating the interior .of bellows 523 with the interior of casing 329 at drain fuel pressure P0. The movable end of bellows 523 is xedly secured to a lever mechanism 52S which is loaded by a. constant reference force derived from a spring 529 acting through a roller 530 which rides between lever 528 pivotally secured to casing 329 and aplate 531 against which spring 529 bears. 'l'he opposite end of spring 529 is supported by :an .adjustable retainer 532 threadedly engaged with casing 329. The roller 530 is rotatably carried by a yoke S33 pivotally secured to rack 505. A lever 528 pivotally secured t-o lcasing 329 and spaced from lever 528 is adapted to engage an end portion of lever 528 as will be described hereinafter. Levers 528 and S28 are preloaded by spr-ings 534 and 535, respectively, which are supported `at one end by adjustable retainers 536 and 537, respectively, threadedly engaged wit-h casing 329. A bellows 538 provided with amova'ble closed end is engageable with lever S28' land is anchored at its opposite end to casing 329 and is vented interiorly to passage 483 at regulated pressure Pr via a restricted passage 539 .and to the interior 4of casing 329 at drain pressure Po via a passage 540 leading from passage 539 upstream of the restriction the-rein to a passa-ge 541 fomned in a lever member 542 and provided with a servo valve S43 at the discharge end thereof. The lever member 542 is pivotally mounted to casing 329 at 544. A rotatable cam 545 fixedly secured to a shaft 546 which is rotated by throttle lever S4 engages servo valve 543 `and -holds the same closed until a predetermined throttle lever position is attained at which time the servo valve 543 is allowed to open thereby vent- .ling passage 541 to drain pressure PO. A lever 547 pivotally secured at one end to lever member 542 `and pivotal-ly secured at its opposite end to a ratchet member 548 is biased into engagement with a stop rnember 549 on lever 542 -by a spring 550 interposedwbetween lever 547 and va retainer 551 fixedly secured to lever 542. A spring 552 interposedl between casing 329 and lever 547 urges lever 542 toward cam- 545. The ratchet member 548 is provided with a stop 553 inetgral thereto which is urged into engagement with lever `547 by the force of a spring 554 interposed betweenlever 547 `and ratchet member 548. A servo valve 555y Xedly secured to lever 547 coacts with the discharge end of a passagev 556 formed in an extended portion of a servo piston557 which is vented on one side to regu-lated fue] pressure P1- via a passage 558 leading from passage 346 and on the opposite side to fuel at regulated pressure Pr via a restricted passage 559, a passage 560 leading to the outlet side of a spool valve 561, 'and a passage 562 leading from the inlet Vsideof valve 560 to passage 483. A valve member 563 inetgral to servo piston 557 is provided with a passage 564 which serves to connect a passage 565 leading from passage 560 at regulated pressure 1:'r with a passage 566 leading to passage 275 in the main fuel control 43 (FIG- URE 2) which, inv turn, leads to chamber 261 at one side of piston 262. A second passage 567 in valve mem- 'at a constant value.

pressure PD via a passage 576 formed in piston S73 and a servo valve 577 engageable with the discharge end'of passage 576. The servo valve 5-77 is iixedly secured to one end of a lever 578 pivotally secured to casing 329 and provided with an adjustable screw member 579 threadedly engaged therewith which is engaged by a bracket 580 iixedly secured to extension 478. A spring 581 loads lever 578 in a counterclockwise direction. The piston 573 is provided with an integral valve portion 582 which in one position communicates a passage 583 leading from passage 480 at regulated pressure Pr with Aa passage 584 leading to one side of a spring loaded piston 585 which is exposed on its opposite side to drain fuel pressure Po and in a second position, as shown in FIGURE 5, disestablishes said communication and vents passage 584 to drain pressure P0. A stem 586 extending from piston 585 is engageable with one end of a spring biased lever 587 pivotally secured to casing 329 which lever is provided with an opposite end portion 588 enga-geable with upper flats of ratchets 589, 590 and 591 formed on ratchet member 548. A spring biased lever 592 pivotally secured to casing 329 is provided with an end portion 593 engageable with lower ats of ratchets S89, 590 kand 591 and is adapted to be engaged by a stem 594 integral with a spring biased piston 595 having a restriction 596 which provides for drainage or fuel from one iside of piston 595 to the opposite side thereof. Fuel at regulated pressure lr is supplied to one side of piston 595 via a passage 597, .and a passage 598 leading from passage 347. A valve 599 in flow controlling relationship with passage 597 is pivotally secured to a lever 600 which is pivotally secured to casing 329 and actuated by Iraised portions 601, 602 and 603 formed on an extension of rack 412. The rack 412 is actuaed by servo piston 604 one side of which is exposed to regulated pressure Plr via passage 605 leading from passage 598. The opposite side of servo piston 604 communicates with regulated pressure P` via a restricted passage 606 leading from passage 568 and with the interior of casing 3129 at drain pressure V1:'D via a discharge passage 607 formed in an extension 608 integral with piston 604. The flow thro-ugh passage 60-7 and thus the fuel pressure acting upon piston 604 is controlled by a servo valve 609 which ooacts with the clischarge end of passage 607 to vary the effective flow area thereof. The servo valve 609 is fixedly secured to and actuated by :a follower 610 which rides against a second contoured portion of cam 474. A lever 611 pivotally secured to follower 610 at 612 is resiliently held in position-relative to follower 610 by a spring 613 interposed between follower 610 and a spring retainer 6-14 integral with lever 611. A pair of adjustable stop members 616 and 617 threadedly engaged with a lever 61S are adapted to engage lever 611 as will be described. The lever 615 extends int-o engagement with a retaining annulus 618 formed on rod 472 which is actuated by alever 619 pivotally secured at one end to casing 329 and at the opposite end engageable with the end of valve 563. A spring 620 serves to bias the end of rod 472 into engagement with lever 619.

An arm 621 xedly secured to valve 563 is connected to a spool valve 622 which is provided with lands 623 and 624. Depending upon the position of valve 622, land 623 serves to vent passage 449 leading to manifold cut-ot valve 338 to drain pressure Po .as well as passages 625 and 626 leading to valves 338 in boxes 341 and 342, respectively. Also, depending upon the position of valve 622, the passage 449 may -be vented to a passage 627 leading from passage 382 which passage 627 contains a ilow regulating valve 628. A diaphragm 629 iixedly secured to valve 628 responds to the pressure drop across valve 628 which 'acts in opposition to a spring 630 acting against diaphragm 629 to thereby control the position of valve 628 to maintain the pressure drop thereacross With the valve 622 positioned as shown in. HGURE 5, the shut-off valve 338 is held closed by virtue of the passage 626 lbeing vented to passa-ge 627 which permits a continuous flow of pressurized fuel through passage 626 to the valve 338. The continuous fiow of fuel to valve 338 also provides for cooling of the same when closed since the valve 338 may be positioned near t-he engine in an environment of relatively high temperature.

The spool valve 481, FIGURE 6, is provided with a stem 631 which engages a second contoured surface of cam 482. The valve 481 is actuated in one direction from a null position shown to vent fuel at regulated pressure Pr to a passage 632 leading to one side of a servo piston 633 and simultaneously vent a passage 634 leading from the opposite side of piston 633 to the interior of casing 329 at drain pressure P0. Actuation of va-lve 481 in the opposite direction from the null position vents passage 634 to regulated pressure Pr and passage 632 to drain pressure P0. The servo piston 633 is pivotally secured to one end of lever 477 which is pivoted about its connection with extension 478 in response to movement of piston 633.

A fuel pressure signal indicative of afterburner blowout is supplied to the main fuel control 43 from exhaust nozzle cont-rol 70 via a passage 635 leading to passage 148 downstream of solenoid actuated valve 150 (FIG- URE 2). As shown in FIGURES 5 .and 6, the passage 635 is vented to fuel at regulated pressure Pr via a passage 636, a chamber 637 containing a doulble ended valve 638, a passage 639, a spool valve 640 and a passage 641 leading to passage 483 at regulated pressure Pr. The valve 638 is shown in a normally closed positi-on whereby the smaller end thereof cooperates with the discharge end of passage 639 to block flow therethrough. The opposite large end of valve 638 is Ibiased away from an orifice 642 which vents chamber 637 and passage 636 connected thereto to the interior of casing 329 at drain fuel pressure P0. The valve 638 is held in the normally closed position by a lever 643 pivotally secured thereto and pivotally secured to casing 329. Tlhe opposite end of lever 643 is engaged tby :a spring lbiased retaining lmemlber 644 slidably car-ried by casing 329 which retaining member urges lever 643 clockwise thereby closing valve 638. Bracket 580 on extension 478 is provided with an adjustable screw member 645 threaded-ly engaged therewith which in response to movement of extension 478 engages retaining member 644 urging the same toward casing 329 thereby unloading lever 643 and permitting valve 638 to open in response to the fuel at pressure Pr acting against the smaller end thereof which fuel at pressure Pr flows into chamber 637 and acts against the larger end of valve 638 thereby holding valve 638 open. It will be understood that the larger end of Valve 638 is seated by the pressure P, in chamber 637 thereby sealing the vent to drain pressure P0.

A passage 646 containing a check valve 647 communicates passage 636 with one side lof a lan-d portion 648 of spool valve 561. The check valve 647 remains closed until actuated by regu-lated pressure Pr in passage 636 at which time fuel at pressure lr is permitted to flow through check valve 647 to the one side of land portion 648 whereupon valve 561 is actuated to the right as viewed in FIG- URE 6 causing land portion 648 to block communication between passages 562 and 560. In the above mentioned rightward position a secon-d land portion 649 of spool valve 561 ve-nts passage 560 to a passage 6-50 leading to the interior of casing 329 at drain pressure P0. As valve 561 moves rightward, a tapered end portion 651 on Valve 561 moves out of engagement with the discharge end of a passage 652 thereby admitting a sec-ond source of fuel at regu-lated pressure Pr to land portion 648. The passage 652 communicates with passage 346 at regulated pressure Pr via .an annulus 653 in valve 484 and a passage 654.

Fuel at regulated pressure Pr may be lintroduced to passage 646 via a passage 655 containing a spring l-oaded check valve 656 which passage 655 is vented -to passage 641 at regulated pressure P1. by a land portion 657 of valve 640. The valve 640 is connected to and actuated by a rod 658 one end of which :rides in a slotted cam member 659 iixedly secured to and rotated by shaft 475. In Iresponse to certain conditions of opera-tion of the exhaust nozzle gates 27, the cam member 659 is adapted to actuate valve 640 to a position whereby lan-d portion 657 vents passage 655 to passage 641 whereupon check valve 656 is opened and fuel at regulated pressure P, communicated to passage 646 to cause rightward movement of valve 651 in the above mentioned manner.

The two position spool valve 484 is slidable in a bore 660 havin-g reduced diameter end portions 661 and 662 which receive fuel at regulated servo pressure Pr from passage 654 via annulus 653, a radial passage 663 and an axial passage 664 in valve 484. The axial passage 664 is provided with restrictions 665 and 666 which control Ifiow to end portions 661 and 662, respectively. The end portions 661 and 662 are vented to the interior of casing 329 at drain fuel pressure Po via passages 667 and 668, respectively, which are provided with orifices 669 and 670 at the -discharge ends there-of. A dapper 671 pivotally secured to casing 329 moves in one direction to open orifice 670 and close orifice 671 and in the opposite direction to close orifice 670 and open orifice 671. The fiapper 671 is actuated by a fol-lower 672 integral therewith which e11- gages a first contoured portion ofa cam 673 fixedly secured -to shaft 546 and rotated by throttle lever 54. The valve 484 is provided with lands 674 and 675 which, in the position of valve 484 shown in FIGURE 6, are positioned to the right of passages228 and 652, respectively, which permits passage 228 to communicate with passage 483 via annulus 676 `in valve 484 and passage 654 to communicate with passage 652. With valve 484 positioned to the left, lands 674 and 675 block passages 228 and 652, respectively. A spring 677 interposed between casing 329 and valve 484 imposes a preload on valve 484 urging the same toward the left. The valve 484 is provided with opposite beveled end portions 678 and 679 which are engageable with their respective end portions 661 and 662 of bore 660 to thereby disestablish communication between the end portions 661 and 662 and passages 667 and 668, respectively.

OPERATION OF MAIN FUEL CONTROL Assuming the engine 20 to be opera-ting initially at a steady state idle speed, an acceleration to maximum speed without afterburner operation is accomplished in the following nranner. The throttle lever 54 is actuated to its maximum speed position which causes rotation of cam 132 and a corresponding actuation of bell crank 129 in va counterclockwise direction as viewed in FIGURE 2 which, in turn, actuates follower 130 and attached rod 131 causing lever 114 to pivot clockwise. The clockwise movement of lever 114 results in ball valve 116 moving toward valve seat 117 thereby increasing fuel pressure Ps which drives piston 109 toward lthe right as viewed in FIGURE 2 causing lever 107 to move out of engagement with abutment 111 whereupon follower 106 lis urged into engagement with cam portion 99 by spring 110 bearing against lever 107. The follower 106 follows cam portion 99 which is contoured to provide a predetermined acceleration fuel schedule as a function of high pressure compressor speed N2 and compressor inlet temperature T. The follower 106 drives roller 199 toward the left as viewed in FIGURE 2 thereby increasing the effective lever arm of lever 20) through which the force derived from bellows 203 acts I causing the lever 200 to pivot clockwise against the opposing constant reference force derived from spring 207. The resulting increase in area of orifice 94 produces a drop in fuel pressure in chamber 89 causing movement of piston 87 and attached valve 84 and a corresponding increase in area of orifice 81 which, in turn, results in increased fuel to the combustion chambers 35. The roller 199 moves with valve 84 causing an increase in the effecl 9 tive lever arm of lever 200 through whi-ch the constant refe-rence force derived from spring 207 acts thereby balancing the opposing torque derived from bellows 203 acting through lever 200 which results in stabilization of piston 87.

As the engine accelerates in response to the increased fuel flow, the compressor discharge pressure Pc increases and acts against bellows 203 causing a corresponding increase in the force applied through roller 199 to lever 200 which, in turn, results in a torque unbalance on lever 200 and corresponding clockwise movement of the same. As heretofore mentioned, clockwise movement of lever 200 results in upward movement of valve 84 .and a corresponding increase in -fuel flow to the combustion chambers 35. The roller 199 follows valve 84 until the effective lever arm of lever 200 through which the spring 207 acts produces a torque equal and opposite to the opposing torque derived from bellows 203 whereupon lever 200 is stabilized. At a predetermined maximum allowable compressor discharge pressure Pc, the bellows 214 overcomes the force of spring 218 and actuates lever 220 away from passage 221 to bleed the pressure in passage 206 downstream from the restriction 215 to atmospheric air pressure Pa thereby limiting the air pressure Pc acting against bellows 214 accordingly.

As the engine accelerates, the force of centrifugal weights 164 increases as a function of engine speed and unbalances lever 158 in a clockwise direction as viewed in FIGURE 2. The resulting increase in area of valve 157 results in a drop in pressure Ps acting against piston 105 which moves to the left as viewed in FIGURE 2 causing shaft 102 and cams secured thereto to rotate as a function of compressor speed N2. As the cams rotate, the follower 106 follows the `contour of cam portion 99 and controls the movement of valve 84 to provide the desired acceleration fuel flow schedule to the combustion chambers 35. The follower 173 follows cam portion 100 and actuates lever 172 clockwise as viewed in FIGURE 2 which, in turn, drives roller 167 causing an increase in the effective lever arm of lever 158 through which the constant reference force derived from spring 165 acts in opposition to the force of centrifugal weights 164. Thus, the torque derived from centrifugal weights 164 acting through lever 158 is balanced by an equal and opposite torque derived from spring 165 acting through a variable lever arm of lever 158 which variable lever arm varies as a function of compressor speed N2 through movement of piston 105 and cam portion 100. The compressor speed N2 function imposed on cam portions 99 and 100 is modified as a function of compressor inlet temperature Ti by piston 175 which actuates lever 178 to cause translation of cam portions 99 and 100. To this end, the bellows 190 expands with increasing temperature Ti and actuates arm 186 counterclockwise as viewed in FIGURE 2 which, in turn, causes movement of lever 185 and a corresponding increase in area of valve 184. The increase in valve 184 area causes a reduction in fuel pressure PS acting against the larger area end of piston 175 which allows piston 175 to move downward under the inuence of pressure Pr. The lever 185 follows the piston 175 and reduces the area of valve 184, thereby causing an increase` in pressure li's whereupon piston 175 is stabilized. The lever 178 follows the piston 175 and translates cam portions 99 and 100 accordingly. A temperature error may be introduced in the bellows 190 by the tube 195 which is likely to be exposed exteriorly to ambient temperatures significantly lower or higher than the temperature at the compressor inlet probe attached thereto. To compensate for the ambient temperature effect on tube 195, the tube 194 which is not provided with a probe exposed to `compressor inlet temperature T1 like tube 195 but which is exposed to the ambient temperatures extends alongside tube 195 and connects to bellows 193 which has a volume equivalent to that of bellows 190. As the volume of bellows 193 increases in response to an increase in the temperature of tube 194, for example, the bell crank 192 is actuated clockwise as shown in FIGURE 2 causing the roller 187 to move down the beveled surface 188 of member 189 thereby reducing the effective length of cylindrical member 189 an amount equivalent to the axial expansion of bellows which, like bellows 193, expands in response to the increased temperature of its tube 195. A decrease in the temperature to which tubes 194 and 195 are exposed results in counterclockwise movement of bell crank 192 and corresponding movement of roller 187 up the beveled surface 188 thereby increasing the effective length of member 189 an amount equivalent to the axial contention of bellows 190. If the ambient temperature to which the tubes 194 and 195 are exposed remains constant, the roller 187 will remain in position on beveled surface 188 and lever 186 will move in response to expansion of bellows 190 as a function of the compressor inlet temperature Ti only.

The three dimensional cams 233 and 234 are rotated by rack 176 as a function of compressor inlet temperature Ti in response to the actuation of piston 175. The cams 233 and 234 are translated by lever 237 in response to movement of piston member 240 as a function of compresser inlet pressure Pi. To this end, the bellows 248 responds to compressor inlet pressure Pi causing lever 246 to pivot clockwise or counterclockwise depending upon the relative change in pressure Pi. For instance, bellows 248 will contract in response to an increase in pressure Pi causing clockwise movement of lever 246 as viewed in FIGURE 3 which increases the area of valve 245 causing pressure Ps on the longer side of piston 240 to decrease thereby upsetting piston 240 toward the left as viewed in FIGURE 2. The roller 252 follows piston 240 thereby increasing the effective lever arm through which the constant reference force derived from spring 241 acts in opposition to the bellows 248. The increase in effective lever arm results in a torque equal and opposite to the torque derived from bellows 248 acting through lever 246 whereupon the lever 246 is stabilized which, in turn, stabilizes the pressure Ps as necessary to hold piston 240 motionless.

The follower 269 is shown in engagement with cam 233 whereas follower 270 is shown out of engagement with cam 234. However, during engine operation in the nonafterburning range as is the case in the engine acceleration under discussion, the chamber 261 is vented to drain pressure P0 via restriction 260 by virtue of valve 563 being in the position shown in FIGURE 5 whereby passages 565 and 566 are blocked to prevent fuel at regulated pressure Pr from flowing to chamber 261. With pressure P0 in chamber 261, the piston 262 and roller 272 attached thereto are biased to the right by spring 274 permitting lever 268 to pivot clockwise under the influence of spring 272 thereby lifting follower 269 out of engagement with cam 233 and permitting follower 270 to engage cam 234. Thus, as the engine accelerates, the cam 132 is positioned axially by movement of casing 260 in response to the cam 234.

Referring now to the FIGURE 3 and the by-pass valve 282 which maintains a constant predetermined pressure differential P1-P2 across orifice 81, it will be understood that various conventional fuel by-pass valves may be substituted therefor. However, the by-pass valve 282 is adapted to eliminate some of the disadvantages of conventional spring loaded by-pass valves which are subject to error due to fluid pressure unbalance thereacross. To this end, the piston 301 reacts to a drop in pressure diffen. ential P1-P2 occasioned by an increase in area of orifice 81 and moves downward to decrease the effective flow area of valve 282 through which fuel at pressure P1 flows to passage 283 at drain pressure Po thus decreasing the quantity of fuel by-passed. The bellows 293 responds to the aforementioned drop in P1-P2 pressure differential across orilice 81 and actuates lever 292 to cause an increase in area of valve 291 which, in turn, causes an increase in fuel pressure Ps acting against piston 284. The pressure Ps actuates piston 284 and valve 282 'integral thereto downward against the resistance of spring 300 and in a closing direction until the force derived from the pressure differential Ps-P2 acting against piston 284 is balanced by the force of spring 300 at which time the constant predetermined pressure differential P1-P2 exists across orice 81. It will be noted that the reset action of piston 301 on spring 301 eliminates the spring error which would be introduced if the spring 301 was fixed at one end and progressively compressed by piston 284 as the fuel pressure P1 and P2 increased with the differential therebetween maintained constant. In the case of an increase in pressure differential P1-P2 across orifice 81, the abovementioned operation is reversed to thereby increase the by-pass flow as necessary to restore the constant predetermined pressure differential.

In the event of a malfunction of the aforementioned fuel control apparatus such that the fuel control functions impressed on metering valve 84 do not provide the desired fuel schedule to the engine, the emergency fuel control apparatus is brought into operation by means of a manual request or automatic switching means responsive to a condition of operation indicative of said malfunction. In such a case, the solenoid 326 is energized causing valve 325 to move to its open position whereby chamber 322 is vented to drain fuel pressure P which, in turn, creates a pressure drop across restricted passage 323. The valve 303 is unbalanced to the right whereupon the left hand end of valve 303 blocks passage 78 and the right hand end of valve 303 diverts fuel .at pressure P1 into conduit 304. The effective flow 4area of conduit 304 and thus fuel flow through conduit 304 to conduit 44 which leads to combustion chambers 35 is controlled by the valve 305 in response to movement -of throttle lever 54. The valve 305 is contoured to provide an emergency fuel flow schedule which has a relatively large safety margin so as to maintain a variable power output of the engine as a function of throttle lever 54 position without exceeding predetermined maximum allowable limits on engine speed, temperatures and/ or pressures.

The fuel flow through conduit 304 is modified as a function of compressor inlet pressure P1 by the by-pass valve 308 which regulates the pressure differential across valve 305. The by-pass valve 308 is positioned by diaphragm 310 in response to the differential between fuel pressure P1 on the one side of diaphragm 310 and the fuel pressure Ps on the opposite side of diaphragm 310 derived from fuel pressure P1, the latter pressure Ps being controlled by valve 313 in response to bellows 317 actuated by compressor inlet pressure P1. The fuel pressure Ps varies as a function of the area ratio of valve 313 and restriction 314 and, for each position of valve 313, assumes a value intermediate fuel pressures P1 and P2. For a given position of valve 305, the fuel pressure differential P1-P2 will be increased in response to an increase in compressor inlet pressure P1 which acts to collapse bellows 317 accordingly causing valve 313 to open thereby causing a corresponding increase in fuel pressure Ps which, in turn, actuates by-pass valve 308 toward a closed position to effect an increase in fuel pressure P1. The combined forces of spring 311 and pressure Ps acting against diaphragm 310 are balanced by an equal and opposite force derived from the increased fuel pressure P1 acting against diaphragm 310 whereupon by-pass valve 308 is stabilized. A decrease in pressure P1 will result in a decrease in pressure Ps and a corresponding reduction in fuel pressure P1.

The check valve 327 is urged to an open position in response to flow through conduit 304- at which time check valve 83 is urged -to a closed position in response to the spring force applied thereto and fuel pressure P2 downstream therefrom.

The cam portion 98 is contoured to provide a cam rise 22 which decreases as .a function of increasing speed N2 such that, upon high pressure compressor speed N2 approaching the requested maximum value, the follower 113 is displaced -causing lever 114 to pivot counterclockwise as Viewed in FIGURE 2. The servo valve 116 follows lever 114 and moves away from valve seat 117 causing a dr-op in pressure Ps whereupon piston 109 moves to the left accordingly which allows lever 107 to engage abutment member 111. Continued movement of piston 109 to the left results in lever 107 pivoting counterclockwise about the point of contact with abutment member 111 thereby lifting follower 106 olf cam portion 99 and actuating follower 106 away from cam portion 99. As piston 109 follows movement of servo valve 116, the lever 107 and attached follower 106 move accordingly until the followup motion of valve seat 117 relative to servo valve 116 re-establishes the pressure Ps necessary to balance piston 109 at which time the lever 107 and follower 106 arev stabilized. The movement of follower 106 results in movement of roller 199 toward the pivot point of lever 200 and a corresponding reduction in the lever arm through which the force derived from bellows 203 acts. The lever 200 is unbalanced in a counterclockwise direction causing a reduction in area of orifice 94 and a corresponding increase in pressures acting against piston 87 which actuates Avalve 84 in a closing direction thereby reducing fuel flow to the combustion chambers. The roller 199 follows valve 84 causing a reduction in the lever arm through which the force derived from spring 207 acts thereby stabilizing lever 200 which, in turn, effects stabilization of valve 84 and thus fuel flow to the combustion chambers such that the engine is governed at the requested high pressure compressor speed N2.

The abutment member 111 may be adjusted toward or away from screw 112 to elfect a corresponding variation in the ratio of lever arms defined by lever 107 coacting with abutment member 111 which, in turn, causes a corresponding change in the slope of the governor break, as desired. Reference is made to U.S. patent application Serial No. 92,876, filed March 2, 1961, in the name of Howard L. McCombs, Ir. (common assignee) for further details of operation of cam portions 98 and 99 and associated linkage mechanism.

OPERATION OF AFTERBURNER FUEL CONTROL AND EXHAUST NOZZLE CONTROL It will be understood that, prior to initiating after- .in the drawings. For instance, referring to FIGURE 6,

during nonafterburning operation the apper will be held against orilice 670 by the cam 673, :such that valve 484 occupies a position to the left against end portion 661 with lands 674 and 675 blocking passages 228 and 652, respectively. The ratchet member 548 will be held in a down position through levers 542 and 547 by the cam 545 whereby the ratchet 589 is out of engagement with and below the end portion 588 of lever 587. Likewise, the servo valve 555 and piston 557, as well as valve 563 attached to the latter, are at a down position whereby passage 567 in valve 563 is positioned below the adjacent end of passage 571 and valve 563 blocks passage 566 as well as passages 569, 570 and 571. Valve 622 attached to valve 563 is positioned accordingly, such that land 624 is below the adjacent end of passage 449 and the three passages 449, 625 and 626 are vented to passage 627. Valve 370 is urged to an open position by the fuel from pump 77 and fuel ows through passages 368 and 371 to valve 372 which is actuated to an open position thereby permitting fuel to flow to passage 373 from which fuel flows through restriction 366 and pressure regulating valve 333 to passages 331 and 336. The fuel shut-off valves 338, only 011e of which is shown, are pressurized toi a closed position by the fuel flowing through associated restricted passages 447 and 448 and passages 449, 625 and 626. The valve 349 occupies a closed position whereby passage 348 is blocked preventing fuel at regulated pressure Pr from reaching passage 350 which results in valve 345 being closed. The valve 349 is held in a closed position by regulated pressure Pr which is admitted to chamber 352 in response to ilapper valve 357 being biased against orifice 359 by lever 360 which is loaded counterclockwise by spring 363.

Now, assuming that the throttle lever 54 is actuated to the position requesting full afterburner operation, the following sequence will occur. The cam 673 wil rotate in response to movement of the throttle lever 54 causing flappcr 671 to move away from orifice 670 into engagement with orifice 669 as shown in FIGURE 6 whereupon valve 484 is pressurized to the right by the' fuel pressure Pr acting against the total left hand end era of valve 484 in opposition to the force of spring 677 plus fuel pressure Pr acting against the relatively small area of valve 484 exposed to end portion 662 plus the pressure Po actin-g against the remaining right hand end area of valve 484. Lands 674 and 675 are displaced away from passages 228 and 652, respectively, thereby establishing cornmunication between passages 228 and 483 and between passages 654 and 652. However, referring to FIGURE 2, fuel at regulated pressure Pr is not permitted to flow to passage 483 until a predetermined high pressure compressor speed N2 is reached at which time the arm 232 carried by piston 105 engages lever 230 causing valve 227 to move upward, thereby communicating passage 226 with passage 228. The resultin-g ow through passage 228 and 483 permits pressurizatio-n of the various servo lines in .afterburner fuel control 55 and` exhaust nozzle control 70 which receive fuel at pressure Pr from passage 483.

Referring to FIGURE 5, t-he `cam 545, like cam 673, rotates with shaft 546 as a function of throttle lever 54 position. Valve 543 follows a depressed contour of cam 545 allowing lever 542 and attached lever 547 to pivot clockwise `until the upper flat of ratchet 589 engages end portion 588 of lever 587 whereupon levers 542 and 547 are held stationary. Fuel at pressure P, flows through passages 560 and 559 to the bottom side of piston 557 thereby urging piston 557 and attached valve 563 upward to a position whereby passage 567 communicates with passage 571. As the piston 557 moves upward away from valve 555, the ow out of passage 556 increases causing a drop in fuel pressure at the bottom side of piston 557 and subsequent stabilization of piston 557. The valve 622 is actuated upward by valve 563 to a position whereby land 624 vents passage 449 to drain fuel pressure Po. Venting passage 449 to drain fuel pressure 1:0 results in a drop in pressure in chamber 445 whereupon shut-olf valve 338 (FIGURE 4) opens in response to metered fuel pressure P3 in conduit 336 thereby allowing fuel to flow to conduit 56 which, in turn, supplies afterburner fuel manifold 38. The afterburner fuel flow is ignited by conventional ignition means, not shown.

Referring to FIGURE 5, the lever 471 is pivoted counterclockwise about its connection with follower 473 in response to upward movement of lever 472 which follows the aforementioned upward movement of valve 563 causing valve 470 to move toward passage 462, thereby causing an increase in fuel pressure at the bottom side of piston 461. The piston 461 actuates spool valve 454 upward from the null position shown in FIGURE 5 thereby communicating passage 457 with passage 453 at high fuel pressure and passage 458 with passage 459 at drain fuel pressure which results in downward movement of piston 65 and opening movement of exhaust nozzle gates 27.

As the exhaust gates 27 are controlled in an opening direction, fuel flow to the afterburner fuel manifold 38 is controlled through piston 604 which rotates shaft 403 carrying .cams 402, 451 and 452 (FIGURE 4a). The lever 472, in its upward movement, actuates lever 615 counterclockwise about its connection 612. The stop 616 on lever 615 engages lever 611 urging the same counterclockwise about connection 612 against the resistance of spring 613. The valve 609 moves accordingly toward extension 608 causing a rise in servo fuel pressure against piston 604 which moves downwardly until stabilized by the follow-up action of extension 688 which moves away from valve 609 thereby reducing the servo fuel pressure acting against piston 604. The stops 616 and 617 establish limits on the position of piston 604 as a function of the position of throttle lever 54 between which limits the position of piston 604 is controlled as a function of the position of cam 474 through follower 610.

The position change of exhaust nozzle gates 27 results in feedback movement of flexible link 75 which rotates shaft 475 and fuel flow and nozzle correlation cam 474 secured thereto. The cam 474 actuates follower 473 causing lever 471 to pivot clockwise about its connection with lever 472, thereby moving valve 470 away from passage 462 which, in turn, results in a drop in fuel pressure at the bottom side of piston 461 and corresponding downward movement of spool valve 454 to its null position whereby the exhaust nozzle gates 27 are stabilized. The follower 610 is positioned by its corresponding portion of cam 474 and moves upward allowing lever 611 to pivot about connection 612 and under the influence of spring 613, engage follower 610 whereupon further movement of follower 610 results in pivotal movement of lever 611 about connection 612 between stops 616 and 617 which, in turn, positions valve 609 thereby causing downward movement of piston 604 and a corresponding rotation of cams 402, 451 and 452.

The cam portion 101 (FIGURE 2) schedules turbine pressure ratio as a function of speed N2 and inlet temperature T'by actuating rollerv517 to cause an increase or de-' crease in the effective lever arm of lever 514 through which the spring 519 acts, thereby upsetting valve 513 in a closing or opening direction depending upon the direction of movement of lever 514. The valve 513 controls the fuel pressure acting against piston 506 which moves accordingly to rotate cam 482 which, in turn, positions roller 495. The position of roller 495 determines the pressure ratio PT4/PT7 required to null the lever 489 and servo valve 488 secured thereto. The roller 530 attached to piston 506 provides a position feedback signal which results in a corresponding variation of the effective lever arm of lever 528 to cause a position change of valve 526 which, in turn, modifies the fuel pressure Ps in bellows 515 accordingly to null the lever 514 loaded by bellows 515 in opposition to the spring 519 and thus null the valve 513 which, in turn, results in stabilization of piston 506.

If the area and fuel ow established by the aforementioned opening movement of exhaust nozzle gates 27 and downward movement of piston 604, respectively, as a function of the position of throttle lever 54 does not establish the pressure ratio Ffm/PT", required to null the lever 489 and servo valve 488, the pressure ratio sensing circuit which includes bellows 492 and 499 and associated linkage actuates the servo valve 488 toward an open or closed position depending upon the relative error in the pressure ratio PT4/PT7. For instance, assuming the pressure PT? downstream of turbine 30 to be in excess of that required to establish the required pressure ratio P114/ PTq, the lever 489 will be unbalanced in a counterclockwise direction thereby actuating valve 488 toward a closed position which, in turn, causes an increase in fuel pressure acting against piston 479 and move-ment toward the right, as viewed in FIGURE 5 of the same. The lever 477 is actuated counterclockwise about its connection with piston 633 by the piston 479 which results in rightward axial movement of cam 474 and subsequent movement of followers 473 and 610 to cause a modification of the area of exhaust nozzle gates 27 and fuel ow, respectively, which have the effect of decreasing pressure PT, thereby correcting the pressure ratio error. The spool valve 454 is nulled in response to feedback movement of flexible link 75 which results in rotation of cam 474. The piston 479 and piston 633 attached thereto via lever 477 provides proportional plus integral operation by means of which the cam 482 is actuated axially to actuate follower 502 and roller 495 attached thereto to a position which satisfies the null requirements of valve 488. The piston 479 provides proportional actuation and the piston 633 provides integrating actuation. Only one axial position of the cam 482 will effect nulling of the valve 481 which controls pressurization of integrator piston 633 which nulling must always occur therefore at the point corresponding to the selected pressure ratio PT4/PT7. The radial contour of cam 482 is constant, such that rotation of cam 482 does affect the position of follower 631. The velocity of the piston 633 is controlled in a conventional manner by controlling the ow of servo fuel thereto as will be readily understood by those persons skilled in the art.

Due to the time delay inherent in hydromechanical contro-l mechanisms of the ytype under di-scussion whereby instantaneous control is not normally available, it is desired to initiate an increase in exhaust nozzle area slightly in advance of ignition of -the lafterburner 'fuel flow to Ithereby lead the resulting increase in pressure PT7 downstream from turbine 30 and hold the pressure ratio Ffm/PTF, relatively stable. To thi-s end, the contour of cam 545 is such that, with ratchet 589 engaged with end portion S88 of lever 587 as mentioned heretofore, the valve 543 is permitted to move away from pas-sage 541 thereby venting the same to drain pressure Po which, in turn, causes a drop in fuel pressure within bellows 538. The bellows 538 contracts thereby allowing lever 528 to contact the end of lever 528 which results in the Aforce of spring 534 acting against lever 528 thereby augmenting the force of spring 529 which lever, in turn, is unbalanced in a counterclockwise direction. The resulting increase in load against bellows 523 results in a corresponding decrease in -ow through tubular member 527 which, in turn, causes an increase in pressure in passage 524 leading to the interior of bellows 515 (FIGURE 2). The bellows 515 expands in response to the increase in pressure therein and unbalances lever 514 in a counterclockwise direction thereby decreasing the ow area of valve 513 which causes a corresponding increase in pressure against the upper side of piston 506 which moves downward as Viewed in FIGURE 6 causing rack 505 to rotate shaft 503 and cam 482 attache-d thereto. The roller 530 moves with rack 505 and decreases the effective lever anm of lever 528 lthrough which the spring 529 acts thereby balancing the opposing torques derived from bellows 523 and spring 534 which results in stabilization of lever 154 and a-ttached valve 513 which, in turn, stabilizes the fuel pressure acting against piston 506 thereby stabilizing the same.

The cam 482 rotates in response to movement of piston 506 and urges follower 582 upwardly causing an increase in the effective lever arm of lever 489 through which bellows 499 acts and subsequent counterclockwise motion of lever 489 which resul-ts in closing movement of valve 488 and a corresponding rise in fuel pressure against the one side of proportionally acting piston 479. The proportionally acting piston 479 moves to the right causing lever 477 to pivot clockwise about its connection with piston 633 and actuate shaft 475 and cam 474 attached thereto to the right. Also, the piston 479 actuates cam 482 to the right causing follower 502 to move downward in response to a depressed contour of cam 482.

The piston v604 is urged downward by the increase in fuel pressure at the top side thereof. Rack 412 attached to piston 604 rotates pinion 413 causing shaft 403 and cams 402, 451 and 452 to rotate correspondingly. It will be understood that fuel is being supplied Ito afterburner manifold 38 only at this time since shut-off valves 338 associated with afterburner fuel manifolds 39 and 40 are closed. The cams 402, 451 and 452 are rotated clockwise looking from the driven end of shaft 403 and are provided with a rising radial c-ontour. Cam 402 rotates driving -follower 401 upward which causes `cam member 399 to pivot counterclockwise thereby lif-ting follower 394 which, in turn, pivots lever 390 -causing valve 385 to move away from passage 387 in valve 334 which results in a drop in fuel pressure PX in chamber 381 and subsequent movement -of valve 334 in an opening direction. As valve 334 moves in an opening direction, passage 387 moves toward valve 386 thereby causing an increase in pressure PX in chamber 381 and -subsequent stabil-ization of valve 334. The bellows 438 responds to the drop in fuel pressure differential across valve 334 caused by opening movement thereof and actuates valve 437 away from passage `436 causing a d-rop in fuel pressure Px at the face 430 of piston 429 thereby actuating valve 335 in an opening direction to Arse-establish lthe predetermined constant pressure differential across valve 334 at which time the valve 335 is stabilized.

The shaft 403 and thus cams 402, 451 and 452 are positioned axial-ly as a function of the inlet temperature sensed by probe 61 which axial movement of cam 402 results in corresponding movement of valve 386 and valve 334 controlled thereby in the above mentioned manner. The position of valve 386 and thus metering valve 334 is modified as a function of compressor inlet pressure Pi which, in an increasing pressure sense, causes bellows 420 to expand thereby opening valve 418 and decreasing the fuel pressure Ps acting on piston 417 which moves to the right cau-sing -counterclockwise movement of lever 414 until the lever 419 and valve 418 attached thereto is stabilized by the follow-up motion of roller 422 attached to piston 417. The movement of lever 414 results in translatory motion of follower 394 which r-otates on shaft 373 in response to the arm 398 following the inclined surface of ramp 399. The rotation of follower 394 results in actuation of lever 390 and corresponding movement of valve 386 and metering valve 334.

Referring back to FIGURE 5 and pist-on 479 which 'move-s to the right in the aforementioned manner, it will Ibe noted that bracket 580 which moves with piston 479 is adapted to engage screw member 579 thereby pivoting lever 578 clockwise causing valve 577 to move away from passage 576 thereby venting the one side of piston 573 to drain fuel pressure Po whereupon the piston 573 is pressurized to lthe right against spring 574 by fuel at regulated pressure Pr acting on the opposite side of piston 573. Movement of piston 573 results in valve 582 integral therewith communicating passage 583 at regulated pressure 1:lr with passage 584 leading to piston 585 which is pressurized against the spring bearing thereagainst causing stem 586 |to engage lever 587 which, in turn, is Ipivoted counterclockwise causing end portion 588 to release ratchet 589 which permits levers 547 and 542 to pivot clockwise. The valve 555 attached to lever 547 moves toward passage 556 causing an increase in pressure at the lbottom -side of piston 557 whereupon piston 557 moves upward displacing valve 563 accordingly. The passage 567 in valve 563 moves out of engagement with passage 571 causing the fuel pressure at the left hand side of piston 573 to drop by virtue of the bleed passage 576 which vents passage 572 to drain fuel pressure Po. The piston 57-3 is biased to the left by spring 574 whereupon valve 582 disestablishes communication between passages 583 and 584 and vents passage 584 to drain fuel pressure P0. The resulting drop in fuel pressure against piston 585' permits retraction of stem 586, allowing lever 587 to pivot clockwise causing end portion 588 thereof to en-gage the upper fiat of ratchet 590 as shown in FIG- URE 5 which fixes the position of lever 547 and valve 555 attached thereto. The piston 557 and valve 563 attached thereto assume a position in accordance with the fixed position of valve 555 such that passage 567 com- 

1. FUEL FLOW CONTROL APPARATUS FOR A GAS TURBINE ENGINE PROVIDED WITH AN AIR COMPRESSOR, AN AFTERBURNER, A PLURALITY OF AFTERBURNER FUEL MANIFOLDS CONNECTED TO DISCHARGE FUEL INTO SAID AFTERBURNER AND A CONTROL LEVEL FOR CONTROLLING THE OPERATION OF THE ENGINE, SAID FUEL CONTROL APPARATUS COMPRISING: A SOURCE OF PRESSURIZED FUEL; A SEPARATE CONDUIT CONNECTED TO SUPPLY FUEL FROM SAID SOURCE TO EACH OF THE FUEL MANIFOLDS; FIRST VALVE MEANS IN EACH OF SAID CONDUITS FOR CONTROLLING THE EFFECTIVE FLOW AREA THEREOF AND THUS FUEL FLOW THERETHROUGH; SECOND VALVE MEANS IN EACH OF SAID CONDUITS RESPONSIVE TO THE FUEL PRESSURE DROP ACROSS SAID FIRST VALVE MEANS FOR CONTROLLING SAID FUEL PRESSURE DROP; A FUEL SHUT-OFF VALVE IN EACH OF SAID FUEL CONDUITS FOR BLOCKING FUEL FLOW THERETHROUGH TO THE ASSOCIATED MANIFOLD; SEPARATE MEANS OPEATIVELY CONNECTED TO EACH OF SAID FIRST VALVE MEANS FOR CONTROLLING THE OPERATION THEREOF; FIRST MEANS RESPONSIVE TO A VARIABLE CONDITION OF ENGINE OPERATION RELATED TO ENGINE POWER OUTPUT OPERATIVELY CONNECTED TO SAID SEPARATE MEANS FOR ACTUATING THE SAME; SECOND MEANS RESPONSIVE TO A VARIABLE CONDITION OF ENGINE OPERATION RELATED TO ENGINE POWER OUTPUT OPERATIVELY CONNECTED TO SAID SEPARATE MEANS FOR ACTUATING THE SAME; THIRD MEANS RESPONSIVE TO THE POSITION OF THE CONTROL LEVER OPERATIVELY CONNECTED TO SAID SEPARATE MEANS FOR ACTUATING THE SAME; MEANS RESPONSIVE TO THE POSITION OF THE CONTROL LEVER OPERATIVELY CONNECTED TO SAID FUEL SHUT-OFF VALVES FOR ACTUATING THE SAME; AND CONTROL MEANS OPERATIVELY CONNECTED TO SAID LAST NAMED MEANS FOR CONTROLLING MOVEMENT THEREOF IN A SERIES OF STEPS TO CAUSE SAID FUEL SHUT-OFF VALVES TO OPEN IN SEQUENCE. 